1. Field of the Invention
The invention relates to a valve device for a catheter with a catheter hub.
2. Description of Related Art
A valve device of the type mentioned before and known from German Patent 30 42 229 C2 serves to introduce elongate objects into a blood vessel through a cannula, and its outer cone is clampingly plugged into the inner cone of the hub. In this case, the valve body consists of a sequence of slotted seal elements, the sealing lips of which abut the elongate objects or each other and close the passages. This valve device can only be used as a sluice for guide wires or the like introduced into the blood vessel from outside. However, it is not suitable for a catheter system for venous applications according to the Seldinger method, wherein the catheter is threaded by its tip over a placed guide wire. This is due to the fact that the frictional forces occurring between the valve body and the guide wire strongly influence the feeling for the placement of the catheter so that the feeling for the placement is lost to a certain extent. Further, it is practically impossible in this valve device to hit the slot of the seal elements with the tip of the guide wire when threading the catheter thereon. Moreover, this known valve device is not suitable for an absolutely secure sealing closure of the passage of a catheter after the removal of the guide wire from its lumen, because the plug connection between the outer cone and the inner cone of the catheter hub is not reliably firm. There is a risk that, in the case of a longer use of a catheter, the plug conection will loosen with the movements of a patient, resulting in air possibly entering the catheter, which may be fatal to the patient if the catheter is placed in a hollow vein. In less dangerous applications, the loosening of the plug connection will cause a leak from which returning body fluid may emerge, leaking from the loosened connection and causing a contamination of the surroundings that might be hazardous to the patient and the personnel.
In another known valve device according to U.S. Pat. No. 4,387,879, similar conditions are encountered that exclude the same from utilisation in a catheter system for venous implementation according to the Seldinger method. A body adapted for limited axial displacement is disposed in a flow channel of a tubular housing, the body cooperating with a disc of elastomeric material shutting off the passage and having an axial slot. The body is designed as a sleeve with a frustoconically tapered end. It is displaced when a connection cone is applied. In doing so, the frustoconical end penetrates the slot in the disc, spreads the same and keeps it open. Thereby, friction between the slots and an elongate element inserted from outside is reduced. To take advantage thereof when threading a venous catheter equipped with this valve device onto the end of a placed guide wire, the body would have to be displaced towards the opening of the slot by means of a connection cone, which cone would in turn impede the placement of the catheter. At one end, the housing of this valve device is provided with an inner cone for the connection cone used to operate the body, and the other end of the housing has a conically tapered stud with continuous ribs that serves to hold a hubless hose pushed thereon and leading to the vessel system. Such a connection between the hose and the valve device is not reliable. Were the valve device to be placed in a conduit system, the connection might become disengaged due to movements and media flowing from or into leaks could cause hazards to the patient and/or the personnel.
It is an object of the invention to provide a valve device that is suitable for use with a catheter system destined for venous applications according to the Seldinger method, and which ensures a reliable sealing of the extracorporal end of the catheter.